.TH "libnvme" 9 "struct nvme_smart_log" "November 2025" "API Manual" LINUX
.SH NAME
struct nvme_smart_log \- SMART / Health Information Log (Log Identifier 02h)
.SH SYNOPSIS
struct nvme_smart_log {
.br
.BI "    __u8 critical_warning;"
.br
.BI "    __u8 temperature[2];"
.br
.BI "    __u8 avail_spare;"
.br
.BI "    __u8 spare_thresh;"
.br
.BI "    __u8 percent_used;"
.br
.BI "    __u8 endu_grp_crit_warn_sumry;"
.br
.BI "    __u8 rsvd7[25];"
.br
.BI "    __u8 data_units_read[16];"
.br
.BI "    __u8 data_units_written[16];"
.br
.BI "    __u8 host_reads[16];"
.br
.BI "    __u8 host_writes[16];"
.br
.BI "    __u8 ctrl_busy_time[16];"
.br
.BI "    __u8 power_cycles[16];"
.br
.BI "    __u8 power_on_hours[16];"
.br
.BI "    __u8 unsafe_shutdowns[16];"
.br
.BI "    __u8 media_errors[16];"
.br
.BI "    __u8 num_err_log_entries[16];"
.br
.BI "    __le32 warning_temp_time;"
.br
.BI "    __le32 critical_comp_time;"
.br
.BI "    __le16 temp_sensor[8];"
.br
.BI "    __le32 thm_temp1_trans_count;"
.br
.BI "    __le32 thm_temp2_trans_count;"
.br
.BI "    __le32 thm_temp1_total_time;"
.br
.BI "    __le32 thm_temp2_total_time;"
.br
.BI "    __u8 rsvd232[280];"
.br
.BI "
};
.br

.SH Members
.IP "critical_warning" 12
This field indicates critical warnings for the state
of the controller. Critical warnings may result in an
asynchronous event notification to the host. Bits in
this field represent the current associated state and
are not persistent (see \fIenum nvme_smart_crit\fP).
.IP "temperature" 12
Composite Temperature: Contains a value corresponding
to a temperature in Kelvins that represents the current
composite temperature of the controller and namespace(s)
associated with that controller. The manner in which
this value is computed is implementation specific and
may not represent the actual temperature of any physical
point in the NVM subsystem. Warning and critical
overheating composite temperature threshold values are
reported by the WCTEMP and CCTEMP fields in the Identify
Controller data structure.
.IP "avail_spare" 12
Available Spare: Contains a normalized percentage (0%
to 100%) of the remaining spare capacity available.
.IP "spare_thresh" 12
Available Spare Threshold: When the Available Spare
falls below the threshold indicated in this field, an
asynchronous event completion may occur. The value is
indicated as a normalized percentage (0% to 100%).
The values 101 to 255 are reserved.
.IP "percent_used" 12
Percentage Used: Contains a vendor specific estimate
of the percentage of NVM subsystem life used based on
the actual usage and the manufacturer's prediction of
NVM life. A value of 100 indicates that the estimated
endurance of the NVM in the NVM subsystem has been
consumed, but may not indicate an NVM subsystem failure.
The value is allowed to exceed 100. Percentages greater
than 254 shall be represented as 255. This value shall
be updated once per power-on hour (when the controller
is not in a sleep state).
.IP "endu_grp_crit_warn_sumry" 12
Endurance Group Critical Warning Summary: This field
indicates critical warnings for the state of Endurance
Groups. Bits in this field represent the current associated
state and are not persistent (see \fIenum nvme_smart_egcw\fP).
.IP "rsvd7" 12
Reserved
.IP "data_units_read" 12
Data Units Read: Contains the number of 512 byte data
units the host has read from the controller; this value
does not include metadata. This value is reported in
thousands (i.e., a value of 1 corresponds to 1000
units of 512 bytes read) and is rounded up (e.g., one
indicates the that number of 512 byte data units read
is from 1 to 1000, three indicates that the number of
512 byte data units read is from 2001 to 3000). When
the LBA size is a value other than 512 bytes, the
controller shall convert the amount of data read to
512 byte units. For the NVM command set, logical blocks
read as part of Compare, Read, and Verify operations
shall be included in this value. A value of 0h in
this field indicates that the number of Data Units Read
is not reported.
.IP "data_units_written" 12
Data Units Written: Contains the number of 512 byte
data units the host has written to the controller;
this value does not include metadata. This value is
reported in thousands (i.e., a value of 1 corresponds
to 1000 units of 512 bytes written) and is rounded up
(e.g., one indicates that the number of 512 byte data
units written is from 1 to 1,000, three indicates that
the number of 512 byte data units written is from 2001
to 3000). When the LBA size is a value other than 512
bytes, the controller shall convert the amount of data
written to 512 byte units. For the NVM command set,
logical blocks written as part of Write operations shall
be included in this value. Write Uncorrectable commands
and Write Zeroes commands shall not impact this value.
A value of 0h in this field indicates that the number
of Data Units Written is not reported.
.IP "host_reads" 12
Host Read Commands: Contains the number of read commands
completed by the controller. For the NVM command set,
this value is the sum of the number of Compare commands
and the number of Read commands.
.IP "host_writes" 12
Host Write Commands: Contains the number of write
commands completed by the controller. For the NVM
command set, this is the number of Write commands.
.IP "ctrl_busy_time" 12
Controller Busy Time: Contains the amount of time the
controller is busy with I/O commands. The controller
is busy when there is a command outstanding to an I/O
Queue (specifically, a command was issued via an I/O
Submission Queue Tail doorbell write and the corresponding
completion queue entry has not been posted yet to the
associated I/O Completion Queue). This value is
reported in minutes.
.IP "power_cycles" 12
Power Cycles: Contains the number of power cycles.
.IP "power_on_hours" 12
Power On Hours: Contains the number of power-on hours.
This may not include time that the controller was
powered and in a non-operational power state.
.IP "unsafe_shutdowns" 12
Unsafe Shutdowns: Contains the number of unsafe
shutdowns. This count is incremented when a Shutdown
Notification (CC.SHN) is not received prior to loss of power.
.IP "media_errors" 12
Media and Data Integrity Errors: Contains the number
of occurrences where the controller detected an
unrecovered data integrity error. Errors such as
uncorrectable ECC, CRC checksum failure, or LBA tag
mismatch are included in this field. Errors introduced
as a result of a Write Uncorrectable command may or
may not be included in this field.
.IP "num_err_log_entries" 12
Number of Error Information Log Entries: Contains the
number of Error Information log entries over the life
of the controller.
.IP "warning_temp_time" 12
Warning Composite Temperature Time: Contains the amount
of time in minutes that the controller is operational
and the Composite Temperature is greater than or equal
to the Warning Composite Temperature Threshold (WCTEMP)
field and less than the Critical Composite Temperature
Threshold (CCTEMP) field in the Identify Controller
data structure. If the value of the WCTEMP or CCTEMP
field is 0h, then this field is always cleared to 0h
regardless of the Composite Temperature value.
.IP "critical_comp_time" 12
Critical Composite Temperature Time: Contains the amount
of time in minutes that the controller is operational
and the Composite Temperature is greater than or equal
to the Critical Composite Temperature Threshold (CCTEMP)
field in the Identify Controller data structure. If
the value of the CCTEMP field is 0h, then this field
is always cleared to 0h regardless of the Composite
Temperature value.
.IP "temp_sensor" 12
Temperature Sensor 1-8: Contains the current temperature
in degrees Kelvin reported by temperature sensors 1-8.
The physical point in the NVM subsystem whose temperature
is reported by the temperature sensor and the temperature
accuracy is implementation specific. An implementation
that does not implement the temperature sensor reports
a value of 0h.
.IP "thm_temp1_trans_count" 12
Thermal Management Temperature 1 Transition Count:
Contains the number of times the controller transitioned
to lower power active power states or performed vendor
specific thermal management actions while minimizing
the impact on performance in order to attempt to reduce
the Composite Temperature because of the host controlled
thermal management feature (i.e., the Composite
Temperature rose above the Thermal Management
Temperature 1). This counter shall not wrap once the
value FFFFFFFFh is reached. A value of 0h, indicates
that this transition has never occurred or this field
is not implemented.
.IP "thm_temp2_trans_count" 12
Thermal Management Temperature 2 Transition Count
.IP "thm_temp1_total_time" 12
Total Time For Thermal Management Temperature 1:
Contains the number of seconds that the controller
had transitioned to lower power active power states or
performed vendor specific thermal management actions
while minimizing the impact on performance in order to
attempt to reduce the Composite Temperature because of
the host controlled thermal management feature. This
counter shall not wrap once the value FFFFFFFFh is
reached. A value of 0h, indicates that this transition
has never occurred or this field is not implemented.
.IP "thm_temp2_total_time" 12
Total Time For Thermal Management Temperature 2
.IP "rsvd232" 12
Reserved
